In Chomsky hierarchy, present computer language grammar is defined as context-free, and Turing machine is defined as the grammar with highest level. Present computer usually processes sequential instructions. In order to execute logic reasoning in artificial intelligent field, PROLOG language needs to search and process horn clauses (rules or facts) in each step. Therefore, search became the largest bottleneck of this language. Since PROLOG possesses the completeness of Turing machine, the computer system that efficiently processes PROLOG is considered to be a Turing machine, or called it “an artificial intelligent computer”.
In 1980's, Japanese government lunched a fifth generation computer project. PROLOG is utilized as major language in this project. In 2011, IBM's supercomputer called “WATSON” had been proved to be more intelligent than human being. Cloud computing technique is used to solve PROLOG problem. WATSON contains nearly 3000 servers in the web. Apple Computer Company's Siri system further applies this technique to people's common life. Such huge and expensive computer system can only be owned by big international enterprise. Robotic technique has good progress in recent years. However, building an affordable intelligent computer system to promote robotic industry still remains a challenging task.